In the last decade Computational Building Performance Simulation (CBPS) has acquired the reputation of a solid analytical method. However, this reputation relies mostly on the admittedly advanced and robust theoretical and algorithmic basis of performance simulation techniques. On the practical side, building simulation has yet to live up to expectation. The main reason is that simulation use is not as widespread as it should. Applications are mostly academic, mainly validation studies. This has led us to the assumption that the applicability and usability of performance simulations require additional components that link them more closely to design processes and facilitate their integration in everyday design activities. In this paper we present the results of research into a working method for location-specific daylight simulation. Our method is based on the satisfication of a number of requirements common to many types of CBPS: validated simulation algorithms, flexible, fast calibration by means of real-world measurement, multiyear, location-specific environmental data, and support of both measured and mathematical environmental data models.